This invention relates to the problem of feeding crushed or pulverized supply material, such as coal or the like (as distinguished from lump coal or the like) from a supply source operating under ambient pressure into a reactor which is operating at a significantly higher pressure. The prior art typically employs either lock hoppers (when working with dry supply material), or slurry systems. For example, lock hoppers comprising a series of pressure locks, operating intermittently and sequentially in connection with systems pumping dry supply material up to reactor pressure are disclosed in U.S. Pat. No. 3,976,443. A major problem of such lock hopper systems is due to rapid deterioration of the cycling hopper valves while working upon the dry erosive supply material.
Slurry systems working with coal employ either a hydrocarbon liquid or water, and for liquefaction processes in which oil is a product of the process this system is generally satisfactory. However, for processes where the product is a gas such as in coal gasification, the use of oil in the slurry would be prohibitively inefficient. Therefore, water slurries have been utilized extensively for such purposes as disclosed by way of example in U.S. Pat. No. 3,976,443. However, as explained in that same patent, the presence of water in the feed mix, due to its high rate of vaporization, reduces the thermal efficiency of the process. Furthermore, the temperatures required for later evaporation of the water content tend to cause the coal to soften, and this in consequence inhibits both the coal dry flow characteristics as well as the process reactions. U.S. Pat. No. 4,261,705 also discloses a supply material handling system which is subject to the same criticisms, and in any case would be applicable only to handling large-sized "lump" coal or the like, as distinguished from methods such as may be suitable when working with crushed or pulverized coal.